Composite Structure Monitoring using Direct Write Sensors

Direct Write (DW) sensors deposited directly and precisely on to complex (3D) components are proposed. Sensors proposed include strain gages and thermocouples, intended as diagnostic elements of a larger health management (HM) scheme. The sensors are deposited using a high precision derivative of thermal spray, affording them the advantages of high temperature tolerance and compatibility with coatings. Strain gages will be deposited as patches onto a range of composites, and laser micromachined to produce their characteristic resistive elements. Signal routing may be via microwelding or DW lead-lines. Thermocouples will be deposited as conformal, parallel traces of paired thermoelements, overlapping to form a junction at the location whose temperature is to be measured. The sensors, having been deposited onto substrates representative of structures on upcoming NASA space vehicles (Orion, Ares, Altair), will then be exposed to conditions similar to those anticipated for said structures, such as low temperatures for fuel tanks, biaxial stress for other pressure vessels, and thermal cycling for on-orbit and lunar exposure. The sensors, having demonstrated their diagnostic capability and compatibility with existing DAQ and HM infrastructures, would form the cornerstone of a potential Phase II continuing application-specific sensor development while expanding to tackle HM integration issues.